JP2012248319A - Fuel cell system and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of maintaining an idling stop state which helps to restrict the degradation of a fuel cell stack over a long period of time, and a method for controlling the fuel cell system.SOLUTION: The fuel cell system includes: idling stop control means which, when a prescribed condition is met during idling power generation, places a stack into an idling stop state by reducing both the amount of air supplied to the stack and the generated current extracted from the stack below those at idling power generation time within a range greater than 0; and exhaust valve control means which determines during idling power generation and idling stop whether nitrogen or generated water in an anode system needs to be ejected and, when determined to be necessary, opens a purge valve or a drain valve for a prescribed valve opening time. In the exhaust valve control means, valve opening times PO2 and DO2 of the purge and drain valves during idling stop are made to be shorter than valve opening times PO1 and DO1 of the purge and drain valves during idling power generation.

Description

  The present invention relates to a fuel cell system and a control method thereof.

  In recent years, fuel cell systems have attracted attention as a new power source for automobiles. The fuel cell system includes, for example, a fuel cell stack that generates electricity by chemically reacting reaction gases (hydrogen and air), and a reaction gas supply device that supplies the reaction gas to the fuel cell via a reaction gas channel. The fuel cell stack has a stack structure in which, for example, several tens to several hundreds of fuel cells are stacked. Here, each fuel cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators, and the membrane electrode structure includes two electrodes, an anode electrode (cathode) and a cathode electrode (anode), A solid polymer electrolyte membrane sandwiched between these electrodes.

  In a fuel cell vehicle using such a fuel cell system as a power source, in order to suppress the consumption of reaction gas as much as possible, for example, when power generation in an idle operation state such as when waiting for a signal is continuously performed, It is preferable to stop the supply of the reaction gas to the fuel cell stack. Patent Document 1 discloses a fuel cell stack and a system by continuing to take out the generated current from the fuel cell stack even after the supply of the reactive gas is stopped, that is, by continuing to discharge the fuel cell stack. There has been proposed a technology that consumes hydrogen and air remaining inside the fuel cell stack, prevents the fuel cell stack from being left in a high voltage state, and thus suppresses deterioration of the fuel cell stack.

JP 2006-294304 A

  However, if the supply of the reactive gas is completely stopped as in the technique of Patent Document 1 above, oxygen staying in the vicinity of the MEA may react with hydrogen and the catalyst may be deteriorated. However, it is known that it is preferable to keep supplying the reaction gas even if very little. Therefore, during idle stop, by supplying the reaction gas at a low flow rate and continuing the discharge, both deterioration due to the reaction of oxygen and hydrogen in the vicinity of the MEA and deterioration due to the high voltage state of the fuel cell stack are prevented. Can be suppressed.

  However, if power generation is continued under such a low flow rate of reactant gas supply, the nitrogen concentration on the anode electrode side tends to increase due to the crossover from the cathode electrode side to the anode electrode side, and the water generated by the power generation is not generated. Since so-called flooding is likely to occur in the reaction gas flow path, the cell voltage tends to decrease. If power generation is continued while the cell voltage is excessively low, the stack may deteriorate, so if the cell voltage drops more than a certain level, the flow rate of the reaction gas is increased to prevent the deterioration from progressing. It is necessary to release the stopped state. For this reason, it is difficult to put the stack in an idle stop state for a long time.

  An object of the present invention is to provide a fuel cell system and a control method for the fuel cell system that can keep the stack in an idle stop state with little deterioration over a long period of time.

  To achieve the above object, the present invention provides a fuel cell (for example, a fuel cell stack 10 to be described later) that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode, and the fuel cell. An electrical load (for example, a high voltage battery 16, a motor 17, and an air pump 21 described later) that consumes the generated power, and an oxidant to the fuel cell in response to a predetermined condition being satisfied during idle power generation Idle stop control means (for example, ECU 40 to be described later) that makes the fuel cell in an idling stop state by reducing both the gas supply amount and the generated current extracted from the fuel cell within a range larger than 0 than during the idle power generation. And) and an anode system through which the gas supplied to the anode electrode and the gas discharged from the anode electrode circulate A discharge valve (for example, a purge valve 351 and a drain valve 361, which will be described later) and a diluting means (for example, a diluting means for diluting the fuel gas discharged from the anode system by opening the discharge valve using an oxidant gas as a diluent gas) A diluter 50), which will be described later, and whether or not the residue in the anode system needs to be discharged during the idle power generation and the idle stop, and if necessary, the discharge valve is turned on for a predetermined time. A fuel cell system (for example, a fuel cell system 1 described later). The discharge valve control means uses the valve opening time (for example, valve opening times PO2 and DO2 in FIG. 10 to be described later) during the idling stop as the valve opening time ( For example, the valve opening time PO1, DO1) in FIG.

In the present invention, even during idle stop, it is necessary to discharge the residue in the anode system, that is, what causes the cell voltage to decrease such as nitrogen and water generated by power generation, as during idle power generation. If necessary, the discharge valve is opened for a predetermined time, and the fuel gas discharged together with the residue is diluted with a dilution gas. As a result, a decrease in the cell voltage can be suppressed, and the idle stop state can be maintained for a long time.
Further, since the oxidant gas is supplied at a lower flow rate during idle stop than in idle power generation, the dilution capability of the fuel gas by the diluting means is reduced. On the other hand, in the present invention, the opening time of the discharge valve during idle stop is made shorter than during idle power generation, so that an amount of fuel gas exceeding the dilution capacity is not introduced into the dilution means. Therefore, according to the present invention, the fuel gas can be sufficiently diluted while maintaining the idling stop state for a long time.

In this case, the time from when the discharge valve is closed until it is opened is defined as a discharge interval, and the discharge valve control means uses the discharge interval during the idling stop (for example, intervals PI2 and DI2 in FIG. 10 described later). The discharge interval during idle power generation (for example, intervals PI1 and DI1 in FIG. 10 described later) is preferably longer.
In the present invention, by setting the discharge interval during idle stop longer than during idle power generation, a sufficient amount of dilution gas is introduced into the diluting means between the previous discharge valve closing and the current discharge valve reopening. be able to.

In this case, the discharge valve control means is one of the two conditions that a predetermined time has passed since the discharge valve was closed and that the integrated value of the generated current taken out from the fuel cell became a predetermined value or more. Alternatively, if both are satisfied, it is preferable to determine that the residue in the anode system needs to be discharged and open the discharge valve.
The elapsed time after closing the discharge valve and the integrated value of the generated current of the fuel cell are considered to be approximately proportional to the integrated amount of dilution gas newly introduced into the dilution means. Therefore, in the present invention, when either or both of the above two conditions are satisfied, the exhaust valve is opened, so that it is sufficient for the diluting means even during idling stop for supplying the oxidant gas at a low flow rate. The discharge valve can be opened at an appropriate timing at which it can be determined that an amount of diluent gas has been introduced.

In this case, it is preferable that the opening time of the discharge valve during the idling stop is set based on the generated current of the fuel cell during the idling stop.
Since the diluting capacity of the diluting means has a correlation with the supply amount of the oxidant gas, and the generated current of the fuel cell has a correlation with the supply amount of the oxidant gas, the present invention opens the exhaust valve during idling stop. The valve time is set based on the generated current of the fuel cell during idle stop. Thereby, the valve opening time of the discharge valve during idling stop can be appropriately set according to the dilution ability by the dilution means.

In this case, the exhaust valve mainly includes a purge valve (for example, a purge valve 351 described later) that discharges mainly gas components out of the residue in the anode system and a liquid component out of residues in the anode system. It is preferable to include at least one of drain valves for discharging (for example, a drain valve 361 described later).
As described above, the residue that causes the cell voltage of the fuel cell during idling to stop includes a gas component such as nitrogen and a liquid component such as water generated by power generation. In the present invention, the purge valve for discharging the gas component is opened / closed at the appropriate valve opening time and discharge interval as described above, thereby suppressing the decrease in the cell voltage due to the increase in the nitrogen concentration and the idle valve. The stop state can be maintained for a long time. In addition, by opening and closing the drain valve for discharging the liquid component at the appropriate valve opening time and discharge interval as described above, the cell voltage drop due to the occurrence of flooding is suppressed, and the idle stop state Can be maintained for a long time.

To achieve the above object, the present invention provides a fuel cell that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode, and an electric load that consumes the power generated by the fuel cell; A discharge valve provided in an anode system through which a gas supplied to the anode electrode and a gas discharged from the anode electrode circulate, and an oxidant gas as a diluent gas, and opening the discharge valve from within the anode system There is provided a control method for a fuel cell system, comprising dilution means for diluting discharged fuel gas. The control method includes an idle power generation step of extracting a generated current of a predetermined magnitude from the fuel cell while supplying a predetermined amount of oxidant gas to the fuel cell, and a predetermined amount during execution of the idle power generation step. An idle stop step that starts in response to the establishment of a condition and extracts a smaller generation current from the fuel cell than in the idle power generation step while supplying a smaller amount of oxidant gas to the fuel cell than in the idle power generation step. And determining whether or not the residue in the anode system needs to be discharged during the idle power generation step and the idle stop step, and if necessary, a discharge step of opening the discharge valve for a predetermined time. In the discharge step, the valve opening time of the discharge valve during the idle stop step is set to be the time of the discharge valve during the idle power generation step. Characterized by shorter than the valve time.
In this case, the time from closing the discharge valve to opening it is defined as the discharge interval, and in the discharge step, the discharge interval during the idle stop step may be longer than the discharge interval during the idle power generation step. preferable.
Further, in this case, in the discharging step, any one of two conditions that a predetermined time has passed since the discharge valve was closed and that the integrated value of the generated current taken out from the fuel cell has become a predetermined value or more. Alternatively, if both are satisfied, it is preferable to determine that the residue in the anode system needs to be discharged and open the discharge valve.
In this case, it is preferable that the opening time of the discharge valve during the idle stop process is set based on the generated current of the fuel cell during the idle stop process.
In this case, the discharge valve is at least one of a purge valve that mainly discharges a gas component of the residue in the anode system and a drain valve that discharges a liquid component of the residue in the anode system. It is preferable to include any of them.
According to the present invention, the same effects as those of the fuel cell system described above can be obtained.

  To achieve the above object, the present invention provides a fuel cell that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode, and an electric load that consumes the power generated by the fuel cell; In response to a predetermined condition being satisfied during idle power generation, the amount of oxidant gas supplied to the fuel cell and the power generation current extracted from the fuel cell are both reduced within a range greater than 0 than during idle power generation. An idle stop control means for bringing the fuel cell into an idle stop state, a discharge valve provided in an anode system through which a gas supplied to the anode electrode and a gas discharged from the anode electrode flow, Diluting means for diluting the fuel gas discharged from the anode system by opening the discharge valve with a diluent gas as a diluent gas, and during idle power generation Open the serial discharge valve for a predetermined time at a predetermined timing during the idle stop provides a fuel cell system and a discharge valve control means for closing the exhaust valve. The idle stop control means is responsive to the fact that the cell voltage of the fuel cell falls below a discharge valve opening threshold corresponding to a cell voltage at which it can be determined that the discharge valve needs to be opened during the idle stop. The stop valve is released and idle power generation is performed, and the discharge valve opening threshold is set to a value larger than a cell voltage at which it can be determined that the deterioration of the fuel cell proceeds.

In the present invention, during idle power generation, the exhaust valve is opened at a predetermined time for a predetermined time, and both the supply amount of oxidant gas to the fuel cell and the generated current to be taken out from the fuel cell are both within a range larger than 0 than during idle power generation. The exhaust valve is closed during idling stop. In addition, according to the present invention, the idle stop is canceled when the cell voltage of the stack falls below the discharge valve opening threshold corresponding to the cell voltage at which it can be determined that the discharge valve needs to be opened during the idle stop. At the same time, the system is set to idle power generation again. Furthermore, the discharge valve opening threshold value is set to a value larger than the cell voltage at which it can be determined that the deterioration of the fuel cell proceeds. That is, according to the present invention, the idle stop can be promptly resumed by releasing the idle stop before a large amount of generated water or nitrogen accumulates in the fuel cell during the idle stop.
For example, when the idling stop is canceled after the cell voltage drops below the cell voltage at which it can be determined that the deterioration of the fuel cell progresses, it is considered that a large amount of generated water or nitrogen has already accumulated in the fuel cell at the time of cancellation. Therefore, it is considered that it takes time to discharge the generated water and nitrogen and to make the idle stop again. On the other hand, in the present invention, by releasing the idling stop more frequently, the time until the idling stop state can be shortened after the release can be shortened. As a result, the fuel cell is put in the idling stop state for a long time. be able to.

  In this case, it is preferable that the discharge valve control means opens the discharge valve for a predetermined time immediately after the idle stop is released.

  When the cell voltage drops to the discharge valve opening threshold during idling stop, it is considered that a certain amount of generated water or nitrogen has already accumulated. In the present invention, the idle valve is opened immediately after the release of the idle stop to efficiently discharge the accumulated generated water and nitrogen, and when the idle stop is resumed, the idle stop state is maintained for a long time. can do.

  In this case, the discharge valve includes at least one of a purge valve that mainly discharges a gaseous component among the residues in the anode system and a drain valve that mainly discharges a liquid component among the residues in the anode system. It is preferable to include.

  In the present invention, the purge valve for discharging the gas component is opened and closed at the timing as described above, thereby suppressing the decrease in the cell voltage due to the increase in the nitrogen concentration and maintaining the idle stop state for a long time. Can do. In addition, by opening and closing the drain valve for discharging the liquid component at the timing as described above, it is possible to suppress a decrease in the cell voltage due to the occurrence of flooding and to maintain the idle stop state for a long time.

1 is a block diagram of a fuel cell system according to a first embodiment of the present invention. It is a time chart which shows an example of the purge control at the time of normal electric power generation of a stack. It is a time chart which shows an example of the procedure of idle stop control. It is a figure which shows the relationship between idle stop continuation time and the nitrogen concentration in an anode system. It is a figure which shows the relationship between idle stop continuation time and the quantity of produced water in an anode system. It is a flowchart which shows the procedure of the purge control in idling stop. It is a figure which shows an example of the map which sets the purge interval threshold value in idling stop. It is a figure which shows an example of the map which sets the valve opening time of the purge valve in idling stop. It is a flowchart which shows the procedure of the drain control in idle stop. It is a time chart which shows the change of the purge valve, the drain valve, and the cell voltage during idling stop. It is a time chart which shows an example of the procedure of the idle stop control of the fuel cell system which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the procedure of purge control. It is a figure which shows an example of the map which sets the request | requirement total purge amount after idle stop cancellation | release. It is a flowchart which shows the procedure of drain control. It is a figure which shows an example of the map which sets the request | requirement total drain amount after idle stop cancellation | release.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of a fuel cell system 1 according to this embodiment.
The fuel cell system 1 includes a fuel cell stack 10, a supply device 20 that supplies the fuel cell stack 10 with hydrogen gas as a fuel gas and air as an oxidant gas, and an electronic control unit that controls the supply device 20 ( (Hereinafter referred to as “ECU”) 40. The fuel cell system 1 is mounted on a traveling fuel cell vehicle (not shown) by driving a motor 17 using electric power generated by the fuel cell stack 10.

  The fuel cell stack (hereinafter simply referred to as “stack”) 10 has a stack structure in which, for example, several tens to several hundreds of cells are stacked. Each cell is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure is composed of two electrodes, an anode electrode (cathode) and a cathode electrode (anode), and a solid polymer electrolyte membrane sandwiched between these electrodes. Usually, both electrodes are formed of a catalyst layer that performs an oxidation / reduction reaction in contact with the solid polymer electrolyte membrane and a gas diffusion layer in contact with the catalyst layer. In the stack 10, when hydrogen gas is supplied to the anode flow path 13 formed on the anode electrode side and oxygen-containing air is supplied to the cathode flow path 14 formed on the cathode electrode side, these electrochemical reactions occur. To generate electricity.

  The supply device 20 includes an air pump 21 that supplies air to the cathode flow path 14 of the stack 10, a hydrogen tank 31 that stores hydrogen gas, and an ejector that supplies the hydrogen gas in the hydrogen tank 31 to the anode flow path 13 of the stack 10. 32.

  The air pump 21 is connected to one end side of the cathode flow path 14 of the stack 10 via the air supply path 22. An air discharge path 23 is connected to the other end side of the cathode flow path 14 of the stack 10, and a diluter 50 serving as a diluting means described later is connected to the front end side of the air discharge path 23. In addition, the air discharge passage 23 is provided with a back pressure valve (not shown) that controls the pressure of the cathode passage 14 of the stack 10.

  The hydrogen tank 31 is connected to one end side of the anode flow path 13 of the stack 10 via a hydrogen supply path 33. An ejector 32 is provided in the hydrogen supply path 33. A shutoff valve (not shown) and a regulator 38 for reducing the pressure of the hydrogen gas supplied from the hydrogen tank 31 are provided between the hydrogen tank 31 and the ejector 32 in the hydrogen supply path 33. The regulator 38 is connected to the flow path 25 branched from the air supply path 22. The pressure in the air supply path 22 is used as a signal pressure, and the hydrogen gas pressure is controlled by opening and closing according to the level of the signal pressure. To do. More specifically, when the pressure in the air supply path 22 increases, the regulator 38 operates on the open side in order to increase the hydrogen gas pressure accordingly.

  A hydrogen reflux path 34 is connected to the other end side of the anode flow path 13 of the stack 10. The distal end side of the hydrogen reflux path 34 is connected to the ejector 32. The ejector 32 collects the hydrogen gas flowing through the hydrogen reflux path 34 and returns it to the hydrogen supply path 33.

  An anode off-gas discharge path 35 is branched from the hydrogen reflux path 34. A diluter 50 is connected to the tip end side of the anode off gas discharge path 35. The anode off gas discharge path 35 is provided with a purge valve 351 that opens and closes the anode off gas discharge path 35 and discharges the hydrogen-containing gas flowing through the hydrogen reflux path 34 to the diluter 50. A detailed procedure of purge control for opening and closing the purge valve 351 at an appropriate timing will be described in detail later.

  The hydrogen recirculation path 34 is provided with a catch tank 37 for storing water generated by power generation discharged from the anode flow path 13 together with the gas component. The catch tank 37 and the diluter 50 are connected by a generated water discharge path 36. The generated water discharge path 36 is provided with a drain valve 361 that discharges the generated water stored in the catch tank 37 to the diluter 50. A detailed procedure of drain control for opening and closing the drain valve 361 at an appropriate timing will be described in detail later.

  The diluter 50 dilutes the hydrogen-containing gas discharged from the stack 10 via the anode off-gas discharge path 35 and the generated water discharge path 36 using the air introduced through the air discharge path 23 as dilution air. More specifically, the diluter 50 opens the purge valve 351 and the drain valve 361 to retain the hydrogen-containing gas discharged together with nitrogen and generated water through the anode off-gas discharge path 35 and the generated water discharge path 36. In addition, the gas in the staying chamber is discharged to the outside of the system while being gradually diluted with dilution air sequentially introduced from the air discharge passage 23.

  In the present embodiment, the gas supplied to the anode flow path 13 of the stack 10 and the anode flow path 13 are discharged from the hydrogen supply path 33, the hydrogen reflux path 34, the anode off-gas discharge path 35, and the generated water discharge path 36. An anode system through which gas flows is configured. Further, the air supply path 22 and the air discharge path 23 constitute a cathode system through which the gas supplied to the cathode flow path 14 of the stack 10 and the gas discharged from the cathode flow path 14 circulate. In FIG. 1, the anode system is indicated by a white arrow, and the cathode system is indicated by a solid arrow.

  The stack 10 is connected to the high voltage battery 16 and the motor 17 via the current controller 15. The high voltage battery 16 stores the electric power generated by the stack 10 and uses it appropriately when the stack 10 is started. The high voltage battery 16 is configured by a secondary battery such as a lithium ion battery or a capacitor, for example. The current controller 15 includes a DC / DC converter, and controls a generated current (hereinafter referred to as “FC current”) taken from the stack 10 based on a current command value determined by the ECU 40. The motor 17 rotates drive wheels (not shown) by the power generated by the stack 10 and the power of the high voltage battery 16.

  In the fuel cell system 1 configured as described above, the air pump 21 for controlling the amount of air supplied to the stack 10, the purge valve 351 for introducing the gas in the anode system to the diluter 50, and the catch tank 37. The drain valve 361 for introducing the generated water into the diluter 50 and the current controller 15 for controlling the FC current are controlled by the ECU 40.

  Next, specific procedures of the purge control, drain control, and idle stop control of the fuel cell system by the ECU will be described with reference to FIGS.

  FIG. 2 is a time chart showing an example of the procedure of purge control. More specifically, it is a time chart showing an example of purge control during normal power generation of the stack. Here, the normal power generation of the stack refers to a state in which the FC current is controlled according to the driver's request for acceleration / deceleration in order to drive and drive the motor using the power generated by the stack.

  While the stack is in the normal power generation state, as shown in FIG. 2, the air supply amount to the stack increases and decreases according to the acceleration / deceleration request by the driver, and the air supply amount to the stack increases and decreases. The FC current also increases or decreases in accordance with. It should be noted that the air supply amount is increased or decreased according to the driver's request, and the FC supply current is increased or decreased during normal power generation. Thus, the fuel supply amount is reduced to a minimum due to a temporary stop of the fuel cell vehicle. In order to distinguish from an idle stop state, which will be described later, this is referred to as an idle power generation state.

  The ECU determines whether opening of the purge valve is permitted while the stack is in normal power generation, determines whether opening of the purge valve is required, and permits opening of the purge valve. Only when required and required, the purge valve is opened for a predetermined valve opening time. A specific procedure for determining whether to open the purge valve and determining whether to open the purge valve will be described below.

  For example, as shown at times t1 to t2 in FIG. 2, when the purge valve is opened, hydrogen gas is introduced into the diluter together with nitrogen remaining in the anode system, so that the hydrogen concentration in the diluter temporarily changes. Get higher. Thereafter, when the purge valve is closed, the hydrogen concentration in the diluter gradually decreases due to the dilution air newly introduced into the diluter. Here, in order to prevent the gas having a high hydrogen concentration from being discharged outside the system, a target value corresponding to the performance is set for the hydrogen concentration in the diluter.

  The ECU permits the opening of the purge valve when it can be determined that the hydrogen concentration in the diluter does not greatly exceed the target value even when the purge valve is opened. More specifically, the ECU calculates a dilution air introduction amount corresponding to the integrated amount of dilution air newly introduced into the diluter after closing the purge valve, and this dilution air introduction amount is predetermined. If the dilution air is less than the required amount, it is determined that the hydrogen in the diluter has not yet been sufficiently diluted and the purge valve is prohibited from opening. The purge valve is allowed to open (see times t3, t5, and t8 in FIG. 2). The dilution air introduction amount is calculated, for example, by integrating the FC current value that is approximately proportional to the amount of air supplied to the diluter.

  The ECU requests opening of the purge valve when it can be determined that the nitrogen concentration in the anode system has increased to some extent. More specifically, the ECU counts a purge interval counter corresponding to the time elapsed since the purge valve was closed, and needs to open the purge valve when the purge interval counter is less than a predetermined purge interval threshold. If the purge interval counter is greater than or equal to the purge interval threshold, it is determined that the purge valve needs to be opened. Note that the purge interval threshold value for determining the request to open the purge valve is set by a predetermined map so as to decrease as the FC current value increases (see a broken line in FIG. 7 described later).

  The ECU determines whether to open the purge valve and whether to open the purge valve as described above. When the opening of the purge valve is permitted and requested (see times t1, t3, t6, and t9 in FIG. 2). ) To open the purge valve for a predetermined opening time. The purge valve opening time (see times t1 to t2, t3 to t4 and t6 to t7 in FIG. 2) is set by a predetermined map so as to increase as the FC current value increases (described later). (See the broken line in FIG. 8).

  As described above, the purge control during normal power generation of the stack has been described with reference to FIG. 2, but since the drain control is performed in the same procedure, the detailed description is omitted. That is, when the drain valve is opened, hydrogen gas is also introduced into the diluter together with the produced water, so that the hydrogen concentration in the diluter does not greatly exceed the target value as in the purge control. When the opening is permitted and requested, the drain valve is opened for a predetermined opening time.

  FIG. 3 is a time chart showing an example of a procedure of idle stop control of the fuel cell system by the ECU. More specifically, from a state in which the fuel cell vehicle is running to a time after stopping at time t0, for example, by waiting for a signal, and the like, until starting driving again at time t2 in response to a driver's acceleration request. It is a time chart which shows changes, such as FC electric current value and air supply amount.

  After the vehicle is temporarily stopped and the supply amount of air and hydrogen gas to the stack is reduced accordingly, the stack enters the above-described idle power generation state (see time t0), and then the ECU In response to the stop start condition being satisfied, the stack is changed from the idle power generation state to the idle stop state (see time t1). More specifically, the stack is brought into an idling stop state by reducing both the rotational speed of the air pump and the FC current in proportion to the amount of air supplied to the stack within a range larger than 0 than during idle power generation. Thereafter, the ECU increases the rotational speed of the air pump as required in response to the predetermined idle stop cancellation condition being satisfied (see time t2).

  Here, the idle stop start condition is, for example, that a predetermined amount of dilution air is introduced into the diluter, but is not limited thereto. Examples of the idle stop cancellation condition include, but are not limited to, an acceleration request by the driver and a cell voltage falling below a predetermined idle stop cancellation threshold (see FIG. 8 described later). Absent. Further, as described above, if power generation is continued in a state where the cell voltage is excessively low, the stack may be deteriorated. Therefore, in order to suppress the deterioration of the stack during the idle stop, the idle stop release threshold for determining the release of the idle stop is set such that the deterioration of the stack may progress if the cell voltage is lower than this. It is set to a value that is considered to be present.

  In addition, the generated current extracted from the stack during idle power generation and idling stop without driving the motor is supplied to, for example, a high voltage battery, supplied to an air pump, or provided separately from these loads. Supplied to the discharge resistor.

FIG. 4 is a diagram showing the relationship between the idle stop duration and the nitrogen concentration in the anode system.
FIG. 5 is a diagram showing the relationship between the idle stop duration and the amount of produced water in the anode system. 4 and 5, the idle stop duration indicates the time during which the idle stop state is continued without opening the purge valve and the drain valve.

  As shown in FIG. 4, the nitrogen concentration in the anode system increases as the idle stop duration time becomes longer due to the crossover from the cathode side to the anode side. Further, when the nitrogen concentration in the anode system exceeds a threshold value as indicated by a broken line in FIG. 4 during idling stop, the cell voltage starts to decrease. As the nitrogen concentration in the anode system becomes higher, the difference between the nitrogen partial pressure on the cathode side and the nitrogen partial pressure on the anode side becomes smaller. Therefore, the increase in the nitrogen concentration becomes slower as the idle stop duration becomes longer.

  In addition, as described above, during idle stop, air is supplied slightly to continue the power generation by the stack, so the amount of generated water also increases. For this reason, as shown in FIG. 5, when the FC current value during idling stop is made constant, the amount of generated water increases in proportion to the idling stop duration. In addition, when the amount of generated water in the anode system exceeds a threshold value as indicated by a broken line in FIG. 5 during idle stop, the cell voltage starts to decrease.

  As described above, when the purge valve and the drain valve are not opened during idling stop, both the nitrogen concentration in the anode system and the amount of generated water increase, and the cell voltage decreases. Therefore, in the present embodiment, in order to maintain the idle stop state for a long time, during the idle stop, purging is performed by a procedure different from the procedure at the time of normal power generation (including idle power generation) described with reference to FIG. Perform control and drain control. Hereinafter, the procedure of purge control and drain control during idle stop will be specifically described.

  FIG. 6 is a flowchart showing the procedure of purge control during idle stop. The process shown in FIG. 6 is repeatedly executed by the ECU every predetermined control period while the idle stop flag indicating that the idle stop is requested is set to “1”. This idle stop flag is set from “0” to “1” in response to the above-described idle stop start condition being satisfied by a process (not shown), and then the above-described idle stop cancellation condition is satisfied. Accordingly, “1” is reset to “0”.

In S1, by searching a predetermined map based on the FC current value, a purge interval threshold value corresponding to a time from closing the purge valve to opening (hereinafter referred to as “purge interval”) is set, and the process proceeds to S2. .
FIG. 7 is a diagram illustrating an example of a map for setting a purge interval threshold value during idling stop. In FIG. 7, an example of a map for setting the purge interval threshold value during normal power generation is shown by a broken line for comparison. As shown in FIG. 7, as the FC current value increases, the purge interval threshold is set to a smaller value. Further, during idling stop, the air supply amount is further reduced as compared with idling power generation as described above, so the purge interval threshold value is set to a larger value compared to idling power generation.

  Returning to FIG. 6, in S2, whether or not the purge interval counter is equal to or greater than the purge interval threshold, that is, whether or not the time corresponding to the purge interval threshold set in S1 has elapsed since the previous purge valve was closed. Determine. If this determination is NO, it is determined that it is not necessary to open the purge valve, and this process is terminated.

If the determination in S2 is YES, it is determined that the purge valve needs to be opened, and the process proceeds to S3. In S3, by searching a predetermined map based on the FC current value, the purge valve opening time is set, and the process proceeds to S4.
FIG. 8 is a diagram showing an example of a map for setting the valve opening time of the purge valve during idling stop. In FIG. 8, an example of a map for setting the opening time of the purge valve during normal power generation is shown by a broken line for comparison. As shown in FIG. 8, the purge valve opening time is set longer as the FC current value increases. Further, during idle stop, as described above, the amount of air supply is further reduced compared to during idle power generation, so that the valve opening time during idle stop is set shorter than the valve opening time during idle power generation.

  In S4, the purge valve is opened over the valve opening time set in S3. In S5, the purge interval counter is reset to “0”, and then this process is terminated.

  FIG. 9 is a flowchart showing a drain control procedure during idle stop. The process shown in FIG. 9 is repeatedly executed by the ECU every predetermined control period while the idle stop flag is set to “1”, similarly to the purge control during the idle stop described with reference to FIG. The

  In S11, by searching a predetermined map based on the FC current value, a drain interval threshold value corresponding to the time from when the drain valve is closed until it is opened (hereinafter referred to as “drain interval”) is set, and the process proceeds to S12. . This drain interval threshold value is set to a smaller value as the FC current value increases, similarly to the purge interval threshold value described with reference to FIG. In addition, during idle stop, the air supply amount is further reduced as compared with that during idle power generation as described above, so the drain interval threshold is set to a larger value than during idle power generation.

  In S12, it is determined whether or not the drain interval counter is equal to or greater than the drain interval threshold, that is, whether or not a time corresponding to the drain interval threshold has elapsed since the drain valve was closed last time. If this determination is NO, it is determined that it is not necessary to open the drain valve, and this process is terminated.

If the determination in S12 is YES, it is determined that the drain valve needs to be opened, and the process proceeds to S13. In S13, by searching a predetermined map based on the FC current value, the valve opening time of the drain valve is set, and the process proceeds to S14. The drain valve opening time is set to become longer as the FC current value increases, similarly to the drain valve opening time described with reference to FIG. Further, during idle stop, as described above, the amount of air supply is further reduced compared to during idle power generation, so that the valve opening time during idle stop is set shorter than the valve opening time during idle power generation.
In S14, the drain valve is opened over the valve opening time set in S13. In S15, the drain interval counter is reset to “0”, and then this process is terminated.

  FIG. 10 is a time chart showing changes in the cell voltage serving as an index of power generation stability of the purge valve, the drain valve, and the stack during idle stop. FIG. 10 shows a case where the stack is placed in the idle stop state after time t1 after the vehicle is temporarily stopped at time t0 and the stack is in the idle power generation state. In FIG. 10, unlike the present embodiment, the change in the cell voltage when the purge valve and the drain valve are not opened during the idling stop is shown by a broken line for comparison.

  First, at time t0, the vehicle is temporarily stopped, so that the stack is in an idle power generation state. In FIG. 10, the amount of air supplied during idle power generation is indicated as R1, and the FC current value is indicated as I1. Further, during idle power generation, purge control and drain control are executed according to the procedure described with reference to FIG. In FIG. 10, the purge interval and drain interval during idle power generation between times t0 and t1 are indicated as PI1 and DI1, respectively, and the opening times of the purge valve and drain valve are indicated as PO1 and DO1, respectively.

  Next, in response to the fact that a predetermined idle stop start condition is satisfied at time t1, the air supply amount is reduced from that during idle power generation (R1 → R2). At this time, the FC current value is also reduced together with the air supply amount from the time of idle power generation (I1 → I2). Thereby, after time t1, the stack enters an idle stop state.

  Immediately after the stack is placed in the idle stop state at time t1, the cell voltage once rises due to the decrease in the FC current value, but both the nitrogen concentration in the anode system and the amount of generated water increase as described above. As a result, the cell voltage starts to decrease (see time t2).

  Here, when neither the purge valve nor the drain valve is opened during the idle stop, the cell voltage gradually decreases and falls below the idle stop release threshold (see time t3) as shown by the broken line in FIG. The idle stop state is released.

  On the other hand, in this embodiment, during idling stop, the purge valve and the drain valve are opened by the procedure described with reference to the flowcharts of FIGS. That is, during idle stop, the air supply amount is reduced. Therefore, the purge valve and drain valve opening times PO2 and DO2 during idle stop are made shorter than the valve opening times PO1 and DO1 during idle power generation. The purge interval PI2 and drain interval DI2 being stopped are set longer than the purge interval PI1 and drain interval DI1 during idle power generation. As a result, as shown in FIG. 10, it is possible to prevent the cell voltage from decreasing until it falls below the idle stop cancellation threshold, and to maintain the idle stop state for a long time.

According to this embodiment, there are the following effects.
(1) In this embodiment, even during idling stop, the purge valve and the drain valve are opened for a predetermined valve opening time, and the hydrogen gas discharged together with nitrogen and generated water is diluted with dilution air. As a result, a decrease in the cell voltage can be suppressed, and the idle stop state can be maintained for a long time. In this embodiment, the opening time of the purge valve and the drain valve during idle stop is made shorter than during idle power generation, so that an amount of hydrogen gas exceeding the dilution capacity is not introduced into the diluter. Therefore, according to the present embodiment, the fuel gas can be sufficiently diluted while maintaining the idling stop state for a long time.

  (2) In this embodiment, by setting the purge interval and drain interval during idle stop longer than during idle power generation, a sufficient amount of dilution can be performed between the previous purge valve and drain valve closing and the current opening again Air can be introduced into the diluter.

  (3) In this embodiment, when the time corresponding to the purge interval threshold elapses after the purge valve is closed, the time corresponding to the drain interval threshold is opened by opening the purge valve or after closing the drain valve. Open the drain valves when they have passed, so that they can be opened at an appropriate timing that can determine that a sufficient amount of dilution air has been introduced into the diluter even during idle stop when supplying air at a low flow rate. Can do.

  (4) In this embodiment, the valve opening time of the purge valve or drain valve during idle stop is set based on the FC current value during idle stop. Thereby, the valve opening time of the purge valve or the drain valve during the idle stop can be appropriately set according to the dilution ability by the diluter.

  (5) In this embodiment, by opening and closing the purge valve at the appropriate valve opening time and purge interval as described above, the cell voltage drop caused by the increase in nitrogen concentration is suppressed, and the idle stop state is set. Can be maintained for a long time. In addition, by opening and closing the rain valve at the appropriate valve opening time and drain interval as described above, it is possible to suppress a decrease in cell voltage due to the occurrence of flooding and to maintain the idle stop state for a long time.

In the above-described embodiment, it is necessary that the time corresponding to the purge interval threshold has elapsed since the purge valve was closed, and when this condition is satisfied during idling stop, it is necessary to discharge nitrogen in the anode system. The purge valve is opened, but the condition for opening the purge valve is not limited to this. In addition, the purge valve may be opened on condition that the integrated value of the FC current is equal to or greater than a predetermined value, or the purge valve may be opened when both of the two conditions are satisfied.
Further, in the above embodiment, it is necessary to discharge the generated water in the anode system when the time corresponding to the drain interval threshold has elapsed since the drain valve was closed and this condition is satisfied during idling stop. The drain valve is opened, but the condition for opening the drain valve is not limited to this. As with the purge valve opening condition, the drain valve may be opened on the condition that the integrated value of the FC current is equal to or greater than a predetermined value, or when both of the above two conditions are satisfied. May be opened.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 11 is a time chart showing an example of a procedure of idle stop control of the fuel cell system by the ECU according to the present embodiment. The present embodiment is different from the first embodiment in the condition for updating the idle stop flag, that is, the idle stop start condition and the idle stop release condition, and the point that the purge valve and the drain valve are not opened during the idle stop.

  In the present embodiment, the idle stop start condition is that the idle stop start condition is that a predetermined amount of dilution air is introduced into the diluter after the stack is in an idle power generation state by temporarily stopping the vehicle. Is satisfied, the stack is changed from the idle power generation state to the idle stop state (see time t1). Further, in this embodiment, the total purge amount corresponding to the total amount of nitrogen exhausted by opening the purge valve after releasing the idle stop exceeds the required total purge amount described later, or the drain valve is opened after releasing the idle stop. The idle stop start condition is that the total drain amount corresponding to the total amount of discharged product water exceeds the required total drain amount described later, and this idle stop start condition is satisfied even after the idle stop is released. Accordingly, the stack is changed from the idle power generation state to the idle stop state again (see time t3). In this way, when the idle stop state is released again after the idle stop is released, until the total purge amount after the idle stop release exceeds the required total purge amount or the total drain amount exceeds the required total drain amount, that is, nitrogen and By continuing the idle power generation until the generated water is sufficiently discharged, it is possible to moderate the decrease in the cell voltage when the idle stop is performed again, so that the idle stop state can be maintained for a long time. .

  In the present embodiment, it is confirmed that the driver has requested acceleration during idle stop, that the cell voltage has fallen below a predetermined valve opening threshold during idle stop, and that the idle stop duration has exceeded a predetermined time limit. As an idle stop cancellation condition, when any of these idle stop cancellation conditions is satisfied during idle stop, the idle stop is canceled (see times t2 and t4). Here, as shown in FIG. 12, the valve opening threshold for the cell voltage is set to a value larger than the idle stop cancellation threshold set to suppress the deterioration of the stack as described above. That is, if there is no acceleration request during idle stop, the idle stop is released earlier than in the first embodiment in the present embodiment. Further, the time limit for the idle stop duration time is determined in advance by a test so as to ensure the stability of the stack during the idle stop or immediately after the release of the idle stop. In this way, by releasing the idle stop according to the idle stop duration, for example, even when the decrease in the power generation stability of the stack during the idle stop does not appear as the decrease in the cell voltage, at an appropriate timing. Since the idle stop can be canceled, the time until the next idle stop after the cancellation can be shortened as much as possible, and as a result, the time for the idle stop can be lengthened.

  The idle stop flag is set from “0” to “1” when the idle stop start condition as described above is satisfied, and from “1” to “0” when the idle stop release condition is satisfied. Reset.

  FIG. 12 is a flowchart showing the procedure of purge control. The process shown in FIG. 12 is repeatedly executed by the ECU every predetermined control cycle after an ignition switch (not shown) is turned on.

In S21, it is determined whether or not the idle stop flag is “1”. If this determination is YES, that is, if idling is currently stopped, the process proceeds to S22, and after calculating the required total purge amount by searching a predetermined map based on the idling stop duration, the purge valve is opened. This process is finished without.
FIG. 13 is a diagram illustrating an example of a map for setting the requested total purge amount after the idle stop is released. As described above, in this embodiment, the purge valve is not opened during idling stop, so the nitrogen concentration in the anode system after the idling stop is released increases in proportion to the idling stop duration. Therefore, as shown in FIG. 13, the required total purge amount is set to increase in proportion to the idle stop duration time.

  When the determination in S21 is NO, that is, when the idle stop is not currently being performed, the process proceeds to S23 to determine whether or not it is immediately after the idle stop is released. If this determination is YES and it is immediately after the current idle stop is released, the process proceeds to S25 and the purge valve is opened for a predetermined time, and then this process is terminated. If the determination in S23 is NO and not immediately after the idle stop is released, the purge valve should be controlled by the same procedure as the purge control during normal power generation described in the first embodiment with reference to FIG. , Go to S24.

  In S24, it is determined whether or not opening of the purge valve is permitted and requested. As described with reference to FIG. 2 in the first embodiment, whether or not opening of the purge valve is permitted is determined by comparing the dilution air introduction amount and the dilution air required amount, Whether or not opening of the purge valve is requested is determined by comparing the purge interval counter with the purge interval threshold value.

  If the determination in S24 is YES, the process proceeds to S25 and the process is terminated after the purge valve is opened for a predetermined valve opening time. If the determination is NO, this process is performed without opening the purge valve. Exit.

  FIG. 14 is a flowchart showing a drain control procedure. The process shown in FIG. 14 is repeatedly executed by the ECU every predetermined control cycle after an ignition switch (not shown) is turned on.

In S31, it is determined whether or not the idle stop flag is “1”. If this determination is YES, that is, if idling is currently stopped, the process proceeds to S32, and after calculating the required total drain amount by searching a predetermined map based on the idling stop duration, the drain valve is opened. This process is finished without.
FIG. 15 is a diagram illustrating an example of a map for setting the requested total drain amount after the idle stop is released. As described above, in this embodiment, the drain valve is not opened during idling stop, so that the amount of generated water in the anode system after the idling stop is released increases in proportion to the idling stop duration time. Therefore, as shown in FIG. 15, the required total drain amount is set to increase in proportion to the idle stop duration.

  When the determination in S31 is NO, that is, when the idle stop is not currently being performed, the process proceeds to S33, and it is determined whether or not it is immediately after the idle stop is released. If this determination is YES and it is immediately after the current idle stop is released, the process proceeds to S35 and the purge valve is opened for a predetermined time, and then this process ends.

  If the determination in S33 is NO and not immediately after the idle stop is released, the process proceeds to S34 in order to control the drain valve by the same procedure as the drain control during normal power generation described in the first embodiment. In S34, it is determined whether or not the opening of the drain valve is permitted and requested. If the determination in S34 is YES, the process proceeds to S35 and the process is terminated after opening the drain valve for a predetermined valve opening time. If the determination is NO, the process is performed without opening the drain valve. Exit.

According to this embodiment, there are the following effects.
(6) In this embodiment, in response to the cell voltage of the stack falling below the valve opening threshold during idle stop, the idle stop is canceled and the idle power generation state is set again. Furthermore, this valve opening threshold value is set to a value larger than the idle stop cancellation threshold value corresponding to the cell voltage at which it can be determined that the deterioration of the stack proceeds. That is, in this embodiment, the idle stop can be promptly resumed by releasing the idle stop before a large amount of generated water or nitrogen accumulates in the stack during the idle stop. For example, when the idle voltage is released after the cell voltage drops below the idle stop release threshold, it is considered that a large amount of generated water or nitrogen has already accumulated in the stack at the time of release. It is thought that it takes time until the engine is discharged again to be in the idle stop state. On the other hand, in the present embodiment, by releasing the idle stop more frequently, it is possible to shorten the time until the idle stop state is resumed after the release, and as a result, the stack is placed in the idle stop state for a long time. be able to.

  (7) In this embodiment, when the purge valve and the drain valve are opened immediately after the release of the idling stop, the accumulated generated water and nitrogen are efficiently discharged, and the idling stop state is resumed for a long time. It is possible to maintain the idle stop state over the entire period.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 10 ... Fuel cell stack (fuel cell)
13 ... Anode channel (anode system)
16 ... High voltage battery (electric load)
17 ... Motor (electric load)
21 ... Air pump (electric load)
33 ... Hydrogen supply path (anode system)
34 ... Hydrogen reflux path (anode system)
35 ... Anode off-gas discharge passage (anode system)
351 ... Purge valve (discharge valve)
36 ... Generated water discharge passage (anode system)
361 ... Drain valve (discharge valve)
40. ECU (idle stop control means)
50 ... Dilutor (dilution means)

Claims (13)

A fuel cell that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode; and
An electric load that consumes the electric power generated by the fuel cell;
In response to a predetermined condition being satisfied during idle power generation, the amount of oxidant gas supplied to the fuel cell and the power generation current extracted from the fuel cell are both reduced within a range greater than 0 than during idle power generation. Idle stop control means for bringing the fuel cell into an idle stop state by
A discharge valve provided in an anode system through which a gas supplied to the anode electrode and a gas discharged from the anode electrode flow;
Diluting means for diluting the fuel gas discharged from the anode system by opening the discharge valve using oxidant gas as a diluent gas,
A discharge valve control means for determining whether or not the residue in the anode system needs to be discharged during the idle power generation and the idle stop, and if necessary, a discharge valve control means for opening the discharge valve for a predetermined time; A fuel cell system comprising:
The exhaust valve control means makes the valve opening time of the exhaust valve during the idling stop shorter than the valve opening time of the exhaust valve during the idle power generation. The time from closing the discharge valve to opening it is defined as the discharge interval,
2. The fuel cell system according to claim 1, wherein the discharge valve control unit makes a discharge interval during the idle stop longer than a discharge interval during the idle power generation.   The discharge valve control means has one or both of two conditions: a predetermined time has elapsed since the discharge valve was closed, and an integrated value of the generated current taken out from the fuel cell became a predetermined value or more. 3. The fuel cell system according to claim 1, wherein when satisfied, it is determined that the residue in the anode system needs to be discharged, and the discharge valve is opened.   4. The fuel cell system according to claim 1, wherein a valve opening time of the discharge valve during the idling stop is set based on a generated current of the fuel cell during the idling stop. 5. .   The discharge valve includes at least one of a purge valve that mainly discharges a gas component of the residue in the anode system and a drain valve that discharges a liquid component of the residue in the anode system. The fuel cell system according to any one of claims 1 to 4, wherein A fuel cell that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode; and
An electric load that consumes the electric power generated by the fuel cell;
A discharge valve provided in an anode system through which a gas supplied to the anode electrode and a gas discharged from the anode electrode flow;
A method for controlling a fuel cell system, comprising: an oxidant gas as a dilution gas; and a dilution means for diluting the fuel gas discharged from the anode system by opening the discharge valve,
An idle power generation step of extracting a generated current of a predetermined magnitude from the fuel cell while supplying a predetermined amount of oxidant gas to the fuel cell;
Starting when the predetermined condition is satisfied while the idle power generation process is being executed, while supplying a smaller amount of oxidant gas to the fuel cell than during the idle power generation process, An idle stop step for extracting a small generated current from the fuel cell;
It is determined whether or not the residue in the anode system needs to be discharged during the idle power generation step and the idle stop step, and if necessary, a discharge step of opening the discharge valve for a predetermined time; Including
In the discharging step, the valve opening time of the discharge valve during the idle stop step is made shorter than the valve opening time of the discharge valve during the idle power generation step. The time from closing the discharge valve to opening it is defined as the discharge interval,
The method of controlling a fuel cell system according to claim 6, wherein in the discharging step, a discharging interval in the idle stop step is made longer than a discharging interval in the idle power generation step.   In the discharging step, one or both of two conditions are satisfied: a predetermined time has passed since the discharge valve was closed, and an integrated value of the generated current taken out from the fuel cell became a predetermined value or more. 8. The method of controlling a fuel cell system according to claim 6 or 7, wherein it is determined that the residue in the anode system needs to be discharged, and the discharge valve is opened.   The fuel according to any one of claims 6 to 8, wherein a valve opening time of the discharge valve during the idle stop process is set based on a power generation current of the fuel cell during the idle stop process. Battery system control method.   The discharge valve includes at least one of a purge valve that mainly discharges a gas component of the residue in the anode system and a drain valve that discharges a liquid component of the residue in the anode system. 10. The method for controlling a fuel cell system according to claim 6, wherein the fuel cell system is a control method. A fuel cell that generates power when fuel gas is supplied to the anode electrode and oxidant gas is supplied to the cathode electrode; and
An electric load that consumes the electric power generated by the fuel cell;
In response to a predetermined condition being satisfied during idle power generation, the amount of oxidant gas supplied to the fuel cell and the power generation current extracted from the fuel cell are both reduced within a range greater than 0 than during idle power generation. Idle stop control means for bringing the fuel cell into an idle stop state by
A discharge valve provided in an anode system through which a gas supplied to the anode electrode and a gas discharged from the anode electrode flow;
Diluting means for diluting the fuel gas discharged from the anode system by opening the discharge valve using oxidant gas as a diluent gas,
A fuel cell system comprising: a discharge valve control means that opens the discharge valve for a predetermined time at a predetermined time during the idle power generation, and closes the discharge valve during the idle stop;
The idle stop control means is responsive to the fact that the cell voltage of the fuel cell falls below a discharge valve opening threshold corresponding to a cell voltage at which it can be determined that the discharge valve needs to be opened during the idle stop. Release the stop and put into idle power generation,
The fuel cell system is characterized in that the exhaust valve opening threshold is set to a value larger than a cell voltage at which it can be determined that deterioration of the fuel cell proceeds.   12. The fuel cell system according to claim 11, wherein the discharge valve control means opens the discharge valve for a predetermined time immediately after the idle stop is released.   The discharge valve includes at least one of a purge valve that mainly discharges a gas component of the residue in the anode system and a drain valve that discharges a liquid component of the residue in the anode system. The fuel cell system according to claim 11 or 12, characterized in that

Images